PNNL

Abstract

This study developed model for predicting viscosity of Hanford low-activity waste (LAW) glass melts as functions of composition and temperature. The model is based on a total of 3935 viscosity-temperature data from 574 glasses with viscosity values ranging from 2.53 to 7260 P in the temperature range from 900 to 1260 °C. Several different model forms were surveyed including those based on Arrhenius, Vogel-Fulcher-Tammann, Avramov-Milchev, and Mauro-Yue-Ellison-Gupta-Allen. For each of these models, combinations of the temperature-independent parameters were fitted to composition. It was found that generally fitting more than one temperature-independent parameter as functions of composition resulted in overfitting. Interestingly, among models where only one parameter is expressed as a function of composition, the best fitting models were those where the composition-dependent parameter is the first one appearing divided by the absolute temperature. The Avramov-Milchev-based model was found to best represent the Hanford LAW glass melt viscosity data based on model fit and validation statistics. A 21-term partial quadratic mixture model was recommended for use. This model predicts melt viscosity with an RMSE = 0.1736 (ln[P]), which is similar to the error in viscosity measurements from replicate glass analyses = 0.1383 (ln[P]). Viscosity was found to be most increased by SiO2 > Al2O3 > ZrO2 > SnO2 and most decreased by Li2O > Na2O > B2O3 > CaO > K2O > MgO, at temperatures from 900 to 1260 °C.